Notes:•The feeding and ground pins have arbitrary positions•To avoid a large capacitance between the two GND planes on the main PCB many viases can be drawn arbitrary•The antenna material can be copper•Antenna bending is allowed. Freedom to choose its size.•Parasitic elements can be applied on one face or the other of the vertical PCB to extend bandwidth•Minimum antenna copper widths >0.5mm•Use parameters for antenna elements size ->Optimetrics can be used to fine-tune the antenna GSM / 3G antenna 824 – 960 MHz &1710 – 2170 MHz

Problem 1:Design a dual band IFA antenna on the vertical PCB from the below picture

- Career opportunities : The easiest way is to …

- to accept challenges like

• PHI & THETA relationships

- Every point in its surrounding is pointed by the position vector r - The magnitude - The inclination (Theta) - The azimuth (Phi)

- It is used for antenna pattern plotting in

3D or 2D (using sections through 3D plot)

28• Antenna feed terminal

- The dipole antenna

29EM wave

30E field along the transmission line

• There is a mutual coupling

between the two line

• When the coupling decreses

the wire begin to radiate through air

• E & H fields can generate

one another in a self sustained manner

31- Front wave is perpendicular to the direction of propagation

60 Pt E  2 Erms R

Erms is the root mean square of E field

3233Pattern along the three regions

34 Antenna basics

- A critical device present in each wireless system

- Energy converter (reciprocal)- Two important distinct regions of the field 2𝐷2 - Near (ends at ) (is interesting for fields 𝜆 applicators in medicine) - Far (here we are going to work in communications and radar field)

- 𝑍𝑖𝑛 = 𝑍0 possible only at resonance

Insertion loss is defined as the ratio of power received at the end of the line and transmitted power source line. It is a size that characterizes the line in terms of losses incurred by the applied signal. In decibels losses are estimated to be as small as possible (0 dB). Its determination taken into account final length of the transmition line, so the effective value is expressed in terms of the line length in dB / m and is positive (the argument of the logarithm lower than one).

𝑃 𝐼𝐿[𝑑𝐵] = −10𝑙𝑔 𝑃𝑅> 0 𝑇

39• Return loss

Insertion loss is defined as the ratio of power received at the end of the line and transmitted power source line. It is a size that characterizes the line in terms of losses incurred by the applied signal. In decibels losses are estimated to be as small as possible (0 dB). Its determination taken into account final length of the transmition line, so the effective value is expressed in terms of the line length in dB / m and is positive (the argument of the logarithm lower than one).

𝑅𝐿[𝑑𝐵] = −10𝑙𝑔 Γ = −10𝑙𝑔𝑆11 > 0

S11 is named in HFSS!

Antenna matching through the load - Tektronics

412. Bandwidth

42Calculation of the antenna frequency band by using the RLif an antenna has two resonant frequencies (dual band)

433. Radiation pattern An antenna radiation pattern or antenna pattern is defined as “a mathematical function or a graphical representation of the radiation properties of the antenna as a function of space coordinates. In most cases, the radiation pattern is determined in the far-field region and is represented as a function of the directional coordinates.

- Its shape depends by the

474. Beamwidth-The beamwidth of a pattern is defined as the angular separation between two identicalpointson opposite sides of the pattern maximum (Pmax – 3 dB HPBW).

SLL-Side lobes level

Polar and cartezian plot

485. Radiation impedance vs input impedanceDefinitionExpression of the antenna radiation resistance is equal, by definition, tothe ratio between the average effective radiated power and average valueof the current that runs through the antenna.

  6,6 x10 6 meters

49• Impedance along the dipol

50 6. Polarization

•The antenna is responsible for the direction and orientation of the vector E (electric field intensity)since the wave is generated in the near field region. If the vector is acting in the horizontal plane, the waveis horizontally polarized, and if it is in the vertical plane, polarization is vertical.

- Nowadays are used more specific polarization usually involves

turning the electric field so that two orthogonal components Etheta and Efi, rotate the tip of E vector. It can describe a circle or an ellipse. Between the two components there is a phase shift which usually distinguish: if phase shift between Eteta and Efi is minus 90 degrees, the two components have equal modules and E vector tip describes a circle, we are dealing with a circular polarization. If the two components meet a phase shift of 180 degrees, we are dealing with a linear polarization. Ultimately, if the phase shift has any other value, different from the two previous cases, we have an elliptical polarization.

51Polarization: elliptical, circular and linear

527. Equivalent area (aperture) and the gainThe power capturing characteristics of the antenna when a wave impinges on it. Theratio of the available power at the terminals of a receiving antenna to the power fluxdensity of a plane wave incident on the.

PR   R AeR

PR is the electric power converted by the antenna at its terminals

R is the power density from its proximity

53DT and DR are the antenna directivities of transmitter and receiver respectively and AeTand AeR are equivalet areas of them.

59Exemple – Design a microstrip patch antenna at 1.6 GHz on a FR4 PCB withelectric permitivity εr = 4.4 having the thickness h = 1.524 mm. The fed line of theantenna has 50 ohms characteristic impedance. After the antenna dimentionmatch the antenna to the 50 ohm characteristic impedance of the fed line.

  eff  0,3  W h   0,264

L  0,412h   0,7 mm   eff  0,258  W h   0,8  

60 0 L  2L  4,43 cm 2  eff

4502 Rin   486 ohmi 2 W

Matching method with a quarter wave line

61• Feeding methods

Input impedance has a real value only at the resonance, this value depends by the conductancevalue from its sides. Mostly the main problem emerges due to the mismatch between the feeding lineand the input impedance of the antenna. In this case a matching impedance must be consider usingstubs on microstrip PCB. Another technique is to resize the width W of the antenna to match the 50ohms characteristic impedance of the feeding line. The antenna admittance is of the form:

Or taking into account the microstrip thickness :

  W  h g ln  g / h  1  

A microtrip patch antenna usually has a reduced aperture even though its radiation efficiency is very high (tends to the unity). When W increases the antenna gain will increase, as well. When we can not modify the W parameter the inset feeding method is an option to keep the impedance matching. The inset feeding technique exploit the variation of the impedance along the antenna (along z axes) variation that follows a co-sinusoidal law :

 z  Rin _ inset  Rin cos 2   Where z is the inset coordinate along the antenna length  L  referring to one of its end

63 This program interface shows this variation of the impedance along the length of the antenna with z.

- inset feed in Ansoft designer)

 Rin _ inset  L 1   z cos   Rin   

64 • Asymmetric feed line method If d is the smallest distance from the edge then theinput admittance could be equated as follows:

b. Inset fed with coaxial line

Electric field bends to the antenna sides making it to looks longer from electric point of view. Voltage wave ismaximum at the ends and the current into the middle. Radiation tends to its maximum in the middle where thecurrent is maximum too.

68•slot coupled antennas

A slot can be used every time the line couldn’t be attached phisically to the patch.

Geometry of the slot can match the input impedance

• VSWR controll

69S11 vs frequency

70From figure we can approximate antenna bandwidth at 18 MHz. The size of the slot can modify the WSVRvalue.

S11 vs frequency (zooming)

71 S11 on Smith chart

•The closer to the origin the better

723D directivity using wire-frame method Slot cupled

73•Half patch antenna – PIFA (Planar Inverted F Antenna- In the middle the input impedance is zero.- Symmetry- Cut the right side and use a short circuit into the middle to force a null- We can shorten the antenna to the half (quarter wavelength)

Normalized depth under the skin

-A group of identic radiators through

-When one can controlled by

software the magnitudes and the phase of the current

82-The very firs applications ofthe EM arrays was in WWII

-Mammut hoarding radar

Modern applications - avionics

83- Equipment is at the cutting edgeof technological advanced - In order to control the magnitude and phase for each radiator the cutting edge of engineering is involving like DSP processing, and software advanced algorithms. A sophisticated software defined radio platform is the key. 84Our technology

The SDR boards from

Sundance and Texas instruments based on the most advanced still cheep DSP’s.

85•A smart antenna is comprised by more arrays of identical radiators (smallantennas) which are connected by means of coaxial or microstrip lines. In the farfield region the resulting field emerges under the effect of the superposition effectof each radiator.•With the help of these lines the direction of the radiation is under the control ofthe signal delay and gain (complex weights) along each path.

Conclusions • The array could be linear (ULA- Uniform linear array) most simple, rectangular or circular (geometry) • To be “smart”, there must be some processing involved before signal summation

86•Antenna feeding network for ULA

87• ULA-Uniform linear array

- There is a phase differences between elements

- Along the front wave the waves are in phase so the direction of the propagation have to make an angle theta that depend by the delay on each path.

- Mean Excess Delay

- RMS – Delay Spread

PT – multipath power gain

- Mean Arrival Angle

- RMS Angular Spread

PAP – Power Angular Profile

Angle of arrival 132

•AoA – Bartlett estimation

- It is among the most simple to be implemented

𝑃𝑏 𝜃 = 𝑎𝐻𝜃 𝑅𝑥𝑥 𝑎 𝜃

𝑃𝑏 𝜃 The probability to find the wave front in that

direction under theta angle

133134135136137• Capone method •This method is well known as Minimum Variance Distortionless Response. Is about finding with the maximum probability (near one) one of the wave front considering all others as interferers.

- Is based on SIR maximization method

138𝑤 𝑇 = 𝑤1 𝑤2 𝑤3 … 𝑤𝑀

−1 𝑅𝑥𝑥 𝑎 𝜃 𝑤= 𝐻 - Calculate the weights for 𝑎 𝜃 𝑅𝑥𝑥 𝑎 𝜃 direction theta to maximize the power for that direction and minimize the power for others

It leads to the following term:

1 𝑃𝐶 𝜃 = 𝑎𝐻𝜃 𝑅𝑥𝑥 𝑎 𝜃

139140Finding the weights

141• Linear prediction method

The main purpose of this method is to minimized the error between one element and a specific one that is the reference for all others.

The reference element is identified using a Cartesian basis vector that

uses number one to mark the reference and zero for all others.

𝑢4𝑇 = 0 0 0 1 0 0 … . . 0

The estimation error is minimized if the reference is near the middle

of the array and the probability to find the incoming front in theta direction is:

𝑇 𝑅 −1 𝑢 𝑢𝑚 𝑥𝑥 𝑚 𝑃𝑃𝐿𝑚 𝜃 = 2 𝑇 −1 𝑢𝑚 𝑅𝑥𝑥 𝑎 𝜃

142143• Burg method

This method is known as the maximum entropy model

1 𝑃𝐵𝑀𝑒𝑗 = 𝑎𝐻𝜃 𝑐𝑗 𝑐𝑗𝐻 𝑎 𝜃

where 𝑐𝑗 is the j’th column of the

−1 . autocorrelation matrix inverse 𝑅𝑥𝑥

InvRx=inv(Rxx); cj=InvRx(:,m)%genereaza coloana j

144145146147148149• Pisarenko method (harmonic decomposition)

- Is about the minimization of the mean square error taking into account that the noise is decorelated with the direction from which the wave fronts coming from. According to Pisarenko the estimation probability of the incoming wave front under theta is:

1 𝑃𝑃𝐻𝐷 𝜃 = 𝑎𝐻 𝜃 𝑒1 2

where 𝑒1 is the eigenvector associated with the lowest eigenvalue 𝜆1 .

150151152153154155•Observatie

1563 Adaptive (smart) antennas

• Adaptive antennas uses beamforming and beamsteering in order to adaptively

improve SNR or SIR parameters.

• Smart beamforming and beamsteering can be accomplished in two different

ways: in RF domain or IF domain. The former is using the RF lines/amplifiers/atenuators (coaxial/microstrip) to alter the signal phase and signal magnitude and the later is using the DSP.

•In IF domain the computational effort is important but leads to the best results.

1573.1. RF domain array processing

• The adaptation methods in RF domain are very effective and cheap for beamforming. For example the most simple and straight RF domain processing is the side lobes suppressing method (with real weights). • Further only the RF domain processing methods with complex weights will be studied.

3.1.1. RF beamforming with Butler labirinth

•Butler discover a method to beamform the radiation of an array using four

hybrid quadrature couplers. No active circuits are required so the processing is very cheap. Is now the most used RF processing for radio cells.

The weights are from the previous table:

3𝜋 𝜋 𝜋 −𝑗 4 −𝑗 4 −𝑗 2 𝑤𝑘1 = 𝑒 ; 𝑤𝑘2 = 𝑒 −𝑗𝜋 ; 𝑤𝑘1 = 𝑒 ; 𝑤𝑘1 = 𝑒

160161There are many possibilities to achieved beamforming by change theposition of the -45 degree delay line or its value.

162Antene pentru microunde - Nicolae 163 Crisan- Hybrid quadrature coupler can be simulated in HFSS, ADS orSysVue in order to counteract the effect of losses in dielectric andbalance the paths against the imbalance effect of the mutual couplingbetween the lines.

•There are to types of smart beamforming

Both of them are demanding a pre-processing step in which case the auto-correlation matrix must be captured.

For both the post-processing step could be done online or offline

The main difference is related to the fact that the former proceeds in time domainand the latter in frequency domain.

The math is similar for both

168169- ABF uses transmition lines- DBF uses DSP’s

The most common beamforming technique is spatial selection

between the beams that are following different paths and arrivingfrom different directions 170- First step starts with the calculation of the AoA using a technique presented in previous chapter- The second step is resolving a linear equations systems

𝐴𝑜𝐴 = [𝜃1 𝜃2 𝜃3 … . 𝜃𝐷 ]

- Let assume that the antenna looks through 𝜃1 direction

- This means AF(𝜃1 ) =1 and for the any other 𝜃2 𝜃3 … . 𝜃𝐷 directions AF=0

Antennas&RFID sensors – 210

Set the conditions required:

𝐴𝑜𝐴 = [ 𝜃1 𝜃2 𝜃3 𝜃4 ] maximum four decorelated fronts

Antennas&RFID sensors – 211

Nicolae Crisan Conclusions• Modern antenna is actively involved in a complex MIMO communications system• Could mitigate efficiently radio channel fading• Introduces an extra dimension that allows the wave front selection and SNR or SIR improvements at the receiver stage• Antenna arrays have a great potential as sensors for radio channel sensing, estimation or sounding• 4G – (LTE and WiMAX) brings new antenna techniques like beamforming and spatial multiplexing Antennas&RFID sensors – Nicolae Crisan 212